Debris barriers are used to prevent particulate buildup in confined spaces that could subsequently impede or prevent operation of other equipment or subsequent relative movement between close fitting components that need to move relatively at some later time. Some applications have no relative movement and the debris barrier is there to isolate equipment such as a liner hanger. Once the hanger is set the debris barrier can be pulled out with the running tool that delivered the liner. On example of this type of annular barrier is shown as item 54 in US Publication 2010/0032167. Another is item 7 in US Publication 20110108266.
Debris barriers can also be placed on whipstocks to keep the whipstock anchor below free of debris as illustrated in U.S. Pat. No. 6,308,782. Debris barriers can be associated with slips so that slip extension energizes a debris barrier such as 34, 164 in U.S. Pat. No. 6,302,217. Annular barriers can be retracted during run in and extended at a desired location with axial compression as with barrier 30 in WO 2008/063979. Debris barriers can be inflatable structures such as item 92 in US Publication 2009/0283330. Debris barriers can temporarily block a tubular string as in item 150 in US Publication 2009/0090518. Applications using sliding sleeves employ debris barriers such as 30b in U.S. Pat. No. 7,032,675. Seals for sliding sleeves are also made from packing material made of continuous carbon fiber in item 30a in the latter patent. On a larger scale such as in a boiler application there are debris barriers internal to the boiler as in item 10 of U.S. Pat. No. 6,581,667.
One such valve that has relatively moving exposed parts to wellbore debris is the RB Isolation Valve offered by Baker Hughes Incorporated, components for which are shown in U.S. Pat. No. 7,210,534 and US Publication 2011/0114324.
What is needed and provided by the present invention is a debris barrier that can exclude most solids from an annular space defined by relatively moving components that might not maintain concentricity during relative movement. The barrier is preferably snap fit and sufficiently loosely mounted so as to enable it to shift and center itself as the shape of the annular space that it blocks changes. It is preferably made of continuous carbon fiber so that it has similar expansion properties as the tubulars that define the annular space where the barrier is mounted. It functions as a bushing using its lubricious properties should the shape of the annular space change due to the tubulars moving out of a concentric relationship. The barrier has an external groove to retain some of the small particles that get between the barrier and the outer tubular that defines the annular space. The part can be made using tight tolerances to maintain very small clearances upon assembly, which is helpful for the exclusion of the solids. The groove can be internal.
Those skilled in the art will have a greater understanding of the invention from a review of the description of the preferred embodiment and the associated drawings while recognizing that the full scope of the invention is determined from the appended claims.